The trend of the automobile industry to improve fuel efficiency by reducing the weight of vehicles has been growing with increased speed in recent years. Amid this trend, the total weight of wires used for each automobile should not be dismissed, and there is also a demand to reduce the weight of wires. Thus, the use of aluminum wires in which aluminum or an aluminum alloy, which are lightweight and inexpensive, is used as wire conductors has become more widespread.
On the other hand, in view of conductivity and the like, copper or a copper alloy is often used as the material for terminal fittings connected to the wires. When a wire conductor and a terminal fitting are made of different materials as in such cases, corrosion due to contact between dissimilar metals occurs at an electrical connection portion therebetween. There is concern that if this corrosion progresses, it may cause an increase in contact resistance and other problems.
In order to prevent such corrosion due to contact between dissimilar metals, it is effective to prevent the intrusion of water and other corrosive substances into a connection portion between the dissimilar metals. JP 2003-297447A and JP 2012-089431A disclose methods in which the periphery of a connection portion between a wire conductor and a terminal fitting is coated with resin.
JP 2003-297447A and JP 2012-089431A are examples of related art.
In a terminal-equipped wire with a resin-coated portion where the periphery of the connection portion is coated with a resin material, if an end portion where the resin-coated portion and the wire are in contact with each other has a steeply rising shape as shown in JP 2003-297447A, when bending stress is applied to the terminal-equipped wire, the resin-coated portion cannot follow the bending, and thus the stress is concentrated in the end portion of the resin-coated portion, which may result in peeling of the coating resin from the wire.
On the other hand, JP 2012-089431A discloses a configuration in which a tapered portion that tapers off toward the wire is provided in the end portion of the resin-coated portion. According to JP 2012-089431A, the stress can be dispersed, and therefore peeling at the end portion can be prevented, by providing the tapered portion. However, as a result of providing the tapered portion, the resin thickness of the end portion decreases, and accordingly, the strength of the end portion of the resin-coated portion decreases. Due to the decrease in strength, there is a risk that the end portion will crack under a large amount of stress.
If the above-described peeling or cracking reaches the connection portion between the wire conductor and the terminal fitting, water and other corrosive substances may intrude through this portion, and there is a risk that corrosion will progress.